1. Field of the Invention
The present invention generally relates to a dynamic damper and a coupling mechanism. In particular, the present invention relates to a dynamic damper which is coupled to an input shaft of a transmission to rotate therewith for dampening vibrations in the coupling mechanism.
2. Background Information
In connection with such a dynamic damper and a coupling mechanism, the assignee has already developed prior arts disclosed in Japanese Laid-Open Patent Publication No. 6-48031 (1994) as well as other similar dynamic dampers and coupling mechanisms.
In the above-mentioned prior arts, a second flywheel forming a mass portion is coupled to a drive and transmission system through a torsional damper mechanism to dampen a torsional vibration on the drive and transmission system only when a clutch disk is pressed against a first flywheel. Thereby, an operation impeding shifting of the transmission is suppressed in a disengaged state of a clutch while suppressing gear noises (neutral noises) of the transmission in a neutral state as well as vibrations and noises of the transmission during driving of a vehicle.
In the above prior arts, a frictional dampening mechanism (sub-clutch) is employed for coupling the second flywheel to the drive and transmission system. The sub-clutch is operated to engage by utilizing an axial movement of the clutch disk which occurs when the clutch disk is pressed against the first flywheel. More specifically, a motion of a spline hub which occurs in accordance with the movement of the clutch disk is utilized to engage frictionally the sub-clutch.
However, the distance of axial movement of the clutch disk is very short. Further, due to deflection of a plate and others which couple the clutch disk to the spline hub, the distance of axial movement of the spline hub is shorter than the distance of axial movement of the clutch disk. Therefore, a member for engaging and disengaging the sub-clutch moves only a small distance. Accordingly, the sub-clutch may operate unstably. For avoiding this unstable operation, the sub-clutch may be adapted to require only a small movement for stable operation. However, this may complicate the structure of the sub-clutch.
In view of the above, there exists a need for a dynamic damper and a coupling mechanism which overcomes these problems in the prior art. This invention addresses these needs in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.